New Biocatalyst Including a 4-Nitrobenzoic Acid Mediator Embedded by the Cross-Linking of Chitosan and Genipin and Its Use in an Energy Device

A new anodic catalyst consisting of carbon nanotube, 4-nitrobenzoic acid, chitosan, genipin, and glucose oxidase (GOx) (CNT/4-NBA/[Chit/GOx/GP]) is suggested to promote the glucose oxidation reaction (GOR) and the performance of enzymatic biofuel cell (EBC). In this catalyst, through the cross-linked structure of chitosan and genipin and the proper distribution of amine groups within chitosan, many GOx molecules are maximally captured, their leaching out is suppressed, and the GOR is improved upon. In addition, 4-nitrobenzoic acid plays the role of mediator well. The effect induced by the cross-linked structure is evaluated by ultraviolet–visible (UV–vis) spectroscopy, pH measurements, and electrochemical characterizations. According to the characterizations, the new CNT/4-NBA/[Chit/GOx/GP] catalyst contains a large amount of GOx (17.8 mg/mL) and produces a high anodic current (331 μA/cm2 at 0.3 V vs Ag/AgCl) with a low onset potential (0.05 V vs Ag/AgCl) because its catalytic activity follows the desirable reaction pathway that minimizes creation of a protonated amine group that interferes with GOR. When the performance of EBC using this catalyst as an anodic electrode is measured, the EBC shows a high open-circuit voltage of 0.54 V and a maximum power density of 38 μW/cm2.